No, I don't know of any. But I know how to find one. Have a search for the term "Leisure Centre". Combine it with "Notting Hill". That should do the job. Many of the hits will be for chain gyms which may allow a short term membership.

If you want outdoor swimming and don't mind a bit of a bus or tube ride there are the ponds on Hampstead Heath, very popular, very natural. You don't say when so you might consider the weather before swimming on the Heath.

Put your postcode into the following site, run for the Amateur Swimming Association: www.swimming.org/poolfinder All kinds of facilities pop up; local authority, university, health clubs etc. with links to their own sites.

Try Porchester Centre (near Bayswater), Queen Mother Sports Centre (near victoria), or Oasis Sports Centre (near Holborn). I haven't been swimming at any of these pools in 10 years, so check web for current info. The Porchester pool was very small, but it is close to Notting Hill.